Aims:
Patients with sickle cell disease (SCD) are often exposed to multiple units of blood transfusions predisposing them to the development of alloantibodies. Alloantibodies make subsequent transfusion difficult, costly and could also result in life-threatening hemolysis. The aim of this study is to estimate and characterize alloantibodies developing over a life-time in patients with sickle cell disease who are on chronic red cell transfusion.
Methods:
Retrospective data were obtained from the electronic medical record and sunquest transfusion record of the DMC for a total of 121 patients with SCD aged 18 years and older who were on chronic red cell exchange transfusion. Data on demographics, blood group, genotype, total number of units transfused over lifetime, presence and type of alloantibodies identified was collected and analyzed.
Results:
The median age of the studied patients was 33 years with a male to female ratio of 0.73. Almost all (>95%) patients had homozygous SCD. A total of 67,586 units were transfused for the 121 patients over a lifetime approximating an average of 559 units transfused per patient. Alloantibodies were identified in 68 of the 121 patients (56.2%). The most common antibody identified was E (27%) followed by K (23%) and C (12%). Overall, antibodies against the Rh system (E, C, D and e) accounted for 39% of the identified antibodies.
Conclusion:
These data demonstrate a high lifetime rate of alloimmunization for patients with SCD on chronic red cell exchange transfusion. Understanding the nature of alloantibody development in chronically transfused SCD patients can help foster appropriate blood utilization paradigms, and develop preventive strategies.

Author Contributions:
Woldie I. – Substantial contributions to conception and design, Acquisition of data, Analysis and interpretation of data, Drafting the article, Revising it critically for important intellectual content, Final approval of the version to be published
Swerdlow P. – Analysis and interpretation of data, Revising it critically for important intellectual content, Final approval of the version to be published
Bluth M.H. – Analysis and interpretation of data, Revising it critically for important intellectual content, Final approval of the version to be published
Mohammad U. – Analysis and interpretation of data, Revising it critically for important intellectual content, Final approval of the version to be published
Landolfi E. – Analysis and interpretation of data, Revising it critically for important intellectual content, Final approval of the version to be published
Chaudrhy S. – Analysis and interpretation of data, Revising it critically for important intellectual content, Final approval of the version to be published
Dyson G. – Analysis and interpretation of data, Revising it critically for important intellectual content, Final approval of the version to be published
O' Malley B.A. – Analysis and interpretation of data, Revising it critically for important intellectual content, Final approval of the version to be published

Guarantor of submission
The corresponding author is the guarantor of submission.